Infrared detection is an optical approach that uses one or more infrared sources in combination with one or more detectors. When measuring concentrations of a particular gas in an atmosphere, the principle is simple: the more gas between a source and detector, the more infrared energy, i.e., light, is absorbed, and thus the transmitted radiation measured by the sensor decreases. Use of the infrared spectrum is often the preferred way to measure gas concentrations in various media, such as atmosphere, blood and various other fluids.
Carbon dioxide has a particularly pronounced absorption peak at 4.26 microns, and thus it can be one of the easier gases to measure in theory. Unfortunately, conventional infrared sources designed to monitor the carbon dioxide peak (by emitted a signal at 4.26 microns) suffer from a variety of problems. For example, the peak wavelength output of IR LEDs often tend to drift with different current levels and variations in temperature. Further, conventional devices rarely, if ever, emit a infrared energy having a profile comparable to the carbon dioxide absorption peak, thus reducing the sensitivity of a detection system. Accordingly, new technology related to infrared sources is desirable.